Hopes fade of finding 13 people, six weeks after Tyva Avia aircraft went missing in remote and mountainous region.

While rescue efforts have been hampered by poor weather, there are no reports of poor conditions other than high winds on the day of the flight last month. Picture: Russian Ministry of Emergencies

A drone has been brought in to help with the increasingly difficult search for a helicopter that crashed last month with 13 people on board. No sign of the Tyva Avia (Tyva Airlines) MI-8 aircraft has been found since it went missing in one of Siberia’s remotest regions, 200km east of Kyzyl, on October 10.

Radio contact was lost as it travelled in a mountainous area between Sorug and the republican capital, and the helicopter's emergency beacon has given out no signal.

A mobile phone ringing on board after the aircraft crashed also did not lead to the location being established.

Officials said a total of 532 people and 61 units of machinery – including aircraft, helicopters and off-road vehicles, have now been used to locate the missing flight, as hopes fade of any survivors being found. A spokesperson for the regional Siberian centre for the Emergencies Ministry said: 'We used a drone yesterday to search in Kaa-Khem area of Tyva. So far it brought no results'.

Adar-ool Norbu (second from the left), one of Siberia's most experienced pilots, himself a hero of a rescue mission last year after six young sportsmen were buried in an avalanche in the republic. Picture: Russian Ministry of Emergencies

While rescue efforts have been hampered by poor weather, there are no reports of poor conditions other than high winds on the day of the flight last month.

An air search for the helicopter has been suspended until the spring, but there is still a search party on the ground trawling the remote snow-covered region for clues as to what happened. The head of the Tyva republic has said a reward will be paid to anyone that can help trace the downed aircraft before the end of the year. However, volunteers seeking to join the official search party have to work with those coordinating the operation.

The helicopter belongs to Tyva Airlines but was being leased for a private purpose.

Most of the passengers on board were employees of 'Stroyline' company (republic of Khakassia), including the director Yuri Shin. Another said to have been on the flight is Alexander Kormilkin, the head of urology at the Khakasia Republican Hospital. It was being piloted by Adar-ool Norbu, one of Siberia's most experienced pilots, himself a hero of a rescue mission last year after six young sportsmen were buried in an avalanche in the republic.

Founded in 1992 and based in Kyzyl, Tyva Airlines is a small company that flies to seven destinations. Tyva borders with the Altai Republic, the Republic of Khakassia, Krasnoyarsk Krai, Irkutsk Oblast, the Republic of Buryatia in Russia, and with Mongolia.